Just after migrating to 1.8.4 full text search did not work
due to an index not properly migrated (I presume)
The error message was something like: can not locate
index that contains those fields:
I workarrounded the problem by changing in fulltext.sql
CREATE FULLTEXT INDEX ft ON tiki_blog_posts (data);
CREATE FULLTEXT INDEX ft ON tiki_blog_posts
dropped the index, and run than script to mysql.